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How is level detected in transparent bottles by a photoelectric detector with relay output?

Within the Schneider range we have dedicated level sensing in the form of XUMW1KSNL2. This is a thru beam sensor which measures the change of beam energy when it has to pass through a liquid in a container. It will work on most containers from clear to near opaque, but not totally opaque. However, this has a solid state output. If a relay output is a required the solid state output could be fed to an interface relay and technically this would be the better solution.

An alternative, cheaper solution is in the form of Thru-beam photoelectric detector XUK0ARCTL2 + XUK0ARCTL2T which has a relay out put and also incorporates delay timing options.

It is recommended that the sensor is set at approximately 20 cm from the bottle. The transmitter is offset in relation to the receiver ( approx 15 mm) so that the receiver does not pick up the beam when passing through the bottle alone. When the liquid reaches the level of the beam it scatters and deflects the beam enough for sufficient light to reach and trigger the sensor.

This part number is only one example. You should choose a sensor to suit the needs of your application.

Whilst this method provides a relatively inexpensive method of level sensing, setting up is very much trial and error. Experimentation will be required to determine the reliability of this method, according to application, liquid and container.